EP0656486B1 - Improvements to hydraulic anti-vibration devices - Google Patents

Description

The invention relates to hydraulic anti-vibration devices intended to be interposed for the purpose of damping and connection, or even support, between two rigid elements such as a vehicle chassis and the engine of this vehicle.

• une armature rigide annulaire et une tige rigide traversant cette armature, solidarisables respectivement avec les deux éléments rigides à réunir,
• un ressort annulaire en élastomère résistant à la compression axiale, reposant sur l'armature et interposé entre celle-ci et la tige, qui le traverse,
• une membrane supérieure flexible et étanche portée par l'armature et délimitant au moins avec une paroi annulaire flexible et étanche une enceinte disposée au-dessus du ressort,
• une cloison rigide intermédiaire portée par l'armature, s'étendant entre la membrane et la paroi annulaire et divisant l'intérieur de l'enceinte en deux chambres, l'une inférieure de travail du côté du ressort et l'autre de compensation,
• un passage étranglé faisant communiquer en permanence les deux chambres entre elles,
• une masse de liquide remplissant les deux chambres et le passage étranglé,
• un premier disque adhéré à la base de la paroi annulaire,
• et un second disque solidaire de la tête de la tige, disposé juste au-dessous du premier disque et reposant sur le ressort.

It relates more particularly, among these devices, those whose construction is generally symmetrical of revolution about a vertical axis and which comprise:

• an annular rigid frame and a rigid rod passing through this frame, which can be secured respectively with the two rigid elements to be joined,
• an annular spring made of elastomer resistant to axial compression, resting on the frame and interposed between the latter and the rod which passes through it,
• a flexible and watertight upper membrane carried by the reinforcement and delimiting at least with a flexible and watertight annular wall an enclosure arranged above the spring,
• a rigid intermediate partition carried by the reinforcement, extending between the membrane and the annular wall and dividing the interior of the enclosure into two chambers, one working lower on the spring side and the other compensating,
• a strangled passageway permanently communicating the two chambers with each other,
• a mass of liquid filling the two chambers and the constricted passage,
• a first disc adhered to the base of the annular wall,
• and a second disc secured to the head of the rod, placed just below the first disc and resting on the spring.

Such devices are known from EP-A-0 575 250 as representing the state of the art according to Article 54 (3) EPC.

In the embodiments of these devices, which have been described in this document, the entire device is subjected, during its assembly, to an axial preload sufficient for the two discs to be permanently applied one against the other. 'other in the axial direction while being able to slide freely relative to each other in the transverse directions.

Due to this permanent application, the two discs can be considered as being joined to one another in the axial direction and the device operates permanently in the manner of a hydraulic support.

In other words, the application on the armature or on the rod, in the axial direction, of oscillations of relatively large amplitude (generally greater than 0.5 mm) and of relatively low frequency (generally of the order from 5 to 20 Hz) - oscillations of the kind of those of "hashes" caused by the bumps of the road during the running of the vehicle concerned-, have the effect of driving the liquid from one of the two chambers into the other and inversely through the constricted passage, with resonance of the liquid mass thus repressed when the frequency of said oscillations reaches a predetermined value which is a function of the ratio between the axial length and the cross section of the constricted passage, this resonance ensuring excellent damping of the oscillations concerned.

This damping is obtained with a relatively high stiffness of the device.

When the device is called upon to operate at a frequency higher than those mentioned above, namely at a frequency of the order of several tens of Hz or even more, as is the case for example when the vehicle engine is running at slowed down to stopping this vehicle, it is necessary to reduce the stiffness of the device as well as its damping, the treatment of vibrations generated by the engine then falling more into insulation or absorption than damping.

For the relatively high frequencies indicated, it would be entirely sufficient for the elasticity of the device to be ensured by the sole spring understood by this device or, in other words, for the hydraulic portion of the device to be neutralized.

The object of the invention is, above all, to make such neutralization easy as soon as the frequency of the oscillations to be treated exceeds a predetermined threshold.

To this end, the anti-vibration devices of the type in question according to the invention are essentially characterized in that they comprise means for controlling at will mutual axial spacings of the two discs and their subsequent contacting.

• les moyens de commande agissent sur la position axiale du centre de la membrane,
• les moyens de commande sont actionnés électriquement,
• les moyens de commande mettent en oeuvre une dépression,
• dans un dispositif selon l'alinéa précédent pour lequel l'un des deux éléments rigides est un moteur de véhicule, la dépression est engendrée par le fonctionnement de ce moteur,
• la commande de l'écartement mutuel des deux disques est asservie au dépassement d'un seuil donné par la fréquence ou par l'amplitude des vibrations imposées à l'une des armatures.

In preferred embodiments, use is also made of one and / or the other of the following arrangements:

• the control means act on the axial position of the center of the membrane,
• the control means are electrically actuated,
• the control means implement a vacuum,
• in a device according to the preceding paragraph for which one of the two rigid elements is a vehicle engine, the vacuum is generated by the operation of this engine,
• the control of the mutual spacing of the two discs is subject to exceeding a threshold given by the frequency or by the amplitude of the vibrations imposed on one of the frames.

The invention includes, apart from these arrangements main, certain other provisions which are preferably used at the same time and which will be more explicitly discussed below.

In what follows, two embodiments of the invention will be described with reference to the attached drawing, of course, in a non-limiting manner.

Figures 1 and 2, of this drawing, show in axial section a first hydraulic anti-vibration device established according to the invention, in respectively its two operating states at relatively low frequency (5-20 Hz) and at high frequency.

Figure 3 similarly shows in Figure 1 but only partially and more schematically, a second hydraulic anti-vibration device according to the invention.

• une armature annulaire rigide 1 d'axe vertical X se présentant sous la forme générale d'un tronçon tubulaire dont l'extrémité inférieure est prolongée radialement vers l'extérieur par une embase annulaire 1₁,
• une tige rigide centrale 2 d'axe X,
• un ressort annulaire en élastomère 3 reposant sur une plaque perforée 1₂ qui est soudée sous l'embase 1₁, ressort interposé verticalement entre ladite plaque et un disque rigide 2₁ solidarisé avec la tête de la tige 2,
• une membrane flexible et étanche 4 supérieure et une paroi annulaire élastique et étanche 5 inférieure fermée à sa base par un disque rigide 6, montées toutes les deux de façon étanche sur l'armature 1, à l'intérieur de la portion supérieure de celle-ci, de manière à former ensemble une enceinte annulaire étanche,
• une cloison intermédiaire rigide 7 portée par l'armature 1, s'étendant entre la membrane 4 et la paroi 5 et divisant l'intérieur de l'enceinte annulaire en deux chambres annulaires, l'une inférieure A, de travail, et l'autre supérieure B, de compensation,
• un passage étranglé 8 évidé dans la cloison 7 et reliant en permanence les deux chambres A et B,
• et une masse de liquide remplissant les deux chambres A et B et le passage étranglé 8.

The first antivibration device illustrated, in FIGS. 1 and 2, has a generally symmetrical shape of revolution around a vertical axis X and comprises:

• a rigid annular reinforcement 1 of vertical axis X having the general form of a tubular section, the lower end of which is extended radially outwards by an annular base 1 ₁ ,
• a central rigid rod 2 of axis X,
• an elastomeric annular spring 3 resting on a perforated plate 1 ₂ which is welded under the base 1 ₁ , spring interposed vertically between said plate and a rigid disc 2 ₁ secured to the head of the rod 2,
• an upper flexible and watertight membrane 4 and a lower elastic and watertight annular wall 5 closed at its base by a rigid disc 6, both mounted in a sealed manner on the frame 1, inside the upper portion thereof ci, so as to form together a sealed annular enclosure,
• a rigid intermediate partition 7 carried by the frame 1, extending between the membrane 4 and the wall 5 and dividing the interior of the annular enclosure in two annular chambers, one lower A, working, and the other upper B, compensation,
• a constricted passage 8 hollowed out in the partition 7 and permanently connecting the two chambers A and B,
• and a mass of liquid filling the two chambers A and B and the constricted passage 8.

It can also be seen in the drawing that the adjacent edges of the membrane 4, of the bellows 5 and of the intermediate partition 6, are crimped on one another in a ring 1 ₃ constituting the upper portion of the frame 1.

The frame 1 and the rod 2 are secured respectively to the two parts between which it is desired to reduce or avoid the transfer of vibrations or oscillations: in the preferred embodiments, the frame 1 is mounted on the body 9 of a vehicle and the rod 2, on the engine 10 of this vehicle, then suspended lower.

The assembly is subjected, during its assembly, to an axial preload sufficient for the two disks 2 ₁ and 6 to be permanently applied one against the other in the direction of the X axis while being able to slide freely l 'relative to each other in the transverse directions.

These two discs are made, at least at their surfaces in mutual contact, of a material having good wear resistance and a coefficient of friction which is either low or to facilitate relative transverse sliding, or high for on the contrary, prevent such slippages.

In the first case, said material is advantageously a polyamide filled with glass fibers and, preferably in addition, with molybdenum disulphide. In the second case, the material in question may be based on rubber.

In addition, the upper membrane 4 is capped with a cover or cover 11 with edges folded down so as to form with this membrane a sealed housing 12: for this purpose, the lower ends of said edges, themselves folded outwards, are crimped with the edges of adjacent parts above mentioned inside the ring 1 ₃ .

The interior of the housing 12 is connected by a pipe 13 with one of the vacuum sources available on the engine 10 in operation, through a valve 15.

• manuelle, et alors commandable par un organe facilement accessible du conducteur du véhicule,
• ou automatique, et par exemple asservie au dépassement d'un seuil donné par la fréquence des oscillations engendrées sur l'un des éléments 9 et 10.

This valve 15, which operates in all or nothing, can be:

• manual, and then controllable by an easily accessible member of the vehicle driver,
• or automatic, and for example subject to the exceeding of a threshold given by the frequency of the oscillations generated on one of the elements 9 and 10.

The operation of the device described above is as follows.

As long as the valve 15 is closed and that consequently no vacuum is applied by the pipe 13 in the housing 12, the two discs 2 ₁ and 6 remain firmly applied axially against each other due to the prestressing mounting and the device operates in the manner of usual hydraulic devices: the relative axial oscillations of the motor 10 relative to the body 9, that is to say of the rod 2 relative to the frame 1 and more precisely of the disc 2 ₁ with respect to the rigid partition 7, result in the comings and goings of liquid between the two chambers A and B through the throttled passage 8 and, for a given value of the frequency of said oscillations, the column of liquid present in the channel 8 enters into resonance, which ensures excellent damping of the oscillations concerned.

As soon as valve 15 is opened, the application in the housing 12 of the vacuum coming from the source 14 has the effect of lifting the membrane 4, which attracts with it upwards the mass of liquid disposed in the assembly of the two chambers A and B with axial contraction of the wall 5 and lifting the disc 6.

As soon as the amplitude of this lifting exceeds the amplitude of the lowering of said disc 6 which was due to the initial mounting preload, a separation of the two discs 2 ₁ and 6 is observed, that is to say the creation of a clearance i (FIG. 2) between these two discs.

Consequently, the hydraulic portion of the device is entirely carried by the single frame 1 and therefore completely neutralized: the elasticity of the support is no longer due to the presence of the spring 3.

This support then has a low stiffness with zero damping, which makes it entirely suitable for isolating vibrations of relatively high frequency.

To pass from the first type of operation to the second, it is advisable to control the valve 15 in such a way that the vacuum is not applied in the housing 12 as long as the frequency of the oscillations to be treated remains relatively low, namely below a predetermined threshold S , which is for example of the order of 20 to 25 Hz, and is applied as soon as said frequency exceeds this threshold.

In preferred embodiments, such a passage can be made automatic and subject to the crossing of the threshold S by the frequency of the oscillations or vibrations to be treated, frequency then detected and measured continuously by an appropriate sensor.

• la dépression appliquée dans le boîtier 12 lors du fonctionnement "haute fréquence" était de l'ordre de 800 millibars,
• le soulèvement global du disque 2₁ résultant de cette application était de l'ordre de 1,5 mm, ce qui correspondait à un jeu résultant i de l'ordre de 0,5 mm, l'abaissement des deux disques 2₁ et 6 accolés dû à la précontrainte de montage étant lui-même de l'ordre du millimètre.

In an embodiment having given all satisfaction and mentioned for purely illustrative purposes,

• the vacuum applied in the housing 12 during "high frequency" operation was of the order of 800 millibars,
• the overall lifting of the disc 2 ₁ resulting from this application was of the order of 1.5 mm, which corresponded to a resulting clearance i of the order of 0.5 mm, the lowering of the two discs 2 ₁ and 6 joined together due to the prestressing of assembly being itself of the order of a millimeter.

In the drawing, we still see at 16 a "valve" mounted so as to be able to vibrate with a limited amplitude - generally less than 1 mm - between two grids 17 and 18 stretched through an orifice 19 hollowed out in the partition 7 and suitable for make the two chambers A and B communicate with each other.

As is known, the vibrations of this valve 16, called "high frequency decoupling", make it possible to absorb vibrations of relatively small amplitude and relatively high frequency, transmitted between the parts 1 and 2.

This improvement increases the possible performance of the anti-vibration device described above.

It makes it possible to choose between two formulas for isolating vibrations at relatively high frequency, namely the use of vacuum which makes it possible to completely neutralize the hydraulic portion of the device or the use of the decoupling valve, which implies an the hydraulic portion and therefore the absence of recourse to a vacuum.

• lorsque cette amplitude est relativement faible -ce qui correspond à un fonctionnement normal du moteur du véhicule- la mise en oeuvre du clapet 16 est tout à fait suffisante, une réduction de la raideur du support étant alors inutile,
• mais lorsque ladite amplitude dépasse un seuil donné -ce qui correspond en particulier au fonctionnement du moteur au ralenti à l'arrêt du véhicule- le clapet risque de venir en butée et il convient d'adopter la première formule, de neutralisation de la portion hydraulique.

In practice, the criterion adopted to make the choice between these two formulas is advantageously the amplitude of the vibrations considered:

• when this amplitude is relatively small - which corresponds to normal operation of the vehicle engine - the use of the valve 16 is entirely sufficient, a reduction in the stiffness of the support then being unnecessary,
• but when said amplitude exceeds a given threshold - which corresponds in particular to the operation from the engine at idle to the stop of the vehicle - the valve risks coming to a stop and it is advisable to adopt the first formula, of neutralization of the hydraulic portion.

The corresponding selection can be easily obtained by slaving the actuation of the valve 15 to the parameters which define said operation of the engine at idle when the vehicle is stopped, and in particular when the vehicle's accelerator pedal is lifted.

It should be noted that the adoption of this last criterion is particularly welcome in the present case, when the vacuum operated is that which prevails just downstream of the throttle valve: it is indeed for the idling operation indicated that this vacuum is the strongest.

The second anti-vibration device illustrated in FIG. 3 differs only from the first in that the control of the displacements of the membrane 4, instead of using a vacuum, is carried out electrically.

To this end, the devices 13 to 15 of FIGS. 1 to 2 are here deleted and the center of the membrane 4 is secured, by means of a rod 20 passing through the center of the cover 11, in an appropriate guide 21, to the core 22 of an electromagnet 23 mounted on this cover 11.

Thus, the assembly of the rod 20 and the membrane 4 is biased upwards when the electromagnet 23 is electrically excited, which separates the disc 6 from the disc 2 ₁ .

On the contrary, when the electromagnet 23 is not electrically excited, said assembly falls back, by simple gravity and / or under the action of a suitable suitable return spring: the two discs 6 and 2 ₁ are then applied again joined one against the other.

The assembly is arranged in such a way that the vertical displacements of the rod 20 are, when the electromagnet 23 is de-energized, sufficiently free so as not to disturb the “compensation” deformations of the membrane 4.

The excitations of the electromagnet 23 of course lend themselves to the same controls as the control of the valve 15 above.

As a result of this, and whatever the embodiment adopted, one finally obtains a device whose constitution, operation and advantages result sufficiently from the above.

• celles où la portion hydraulique comprenant l'ensemble des éléments 4 à 8 ci-dessus décrits présenterait une configuration annulaire autour de l'axe X, ainsi que décrit dans le document EP-A-0 575 250 ci-dessus mentionné, le disque 6 étant alors réduit à une rondelle annulaire,
• celles où la symétrie de révolution du dispositif ne serait que partielle, la section horizontale de l'ensemble pouvant par exemple présenter la forme allongée de deux demi-cercles de diamètres identiques ouverts l'un vers l'autre et raccordés entre eux par deux tronçons de droite parallèles,
• et celles où les écartements des deux disques 2₁ et 6 seraient commandés par des moyens différents de ceux décrits ci-dessus, par exemple à l'aide d'un mécanisme à came rotative et levier actionnable électriquement et lié à une tige du genre de la tige 20 ci-dessus, cette liaison étant prévue avec un jeu tel que, lorsque le mécanisme n'est pas actionné, les déplacements de la membrane 4 soient suffisamment libres.

As goes without saying, and as it already follows from the above, the invention is in no way limited to those of its modes of application and embodiments which have been more especially envisaged; on the contrary, it embraces all variants, in particular:

• those where the hydraulic portion comprising all of the elements 4 to 8 described above would have an annular configuration around the axis X, as described in the document EP-A-0 575 250 above mentioned, the disc 6 then being reduced to an annular washer,
• those where the symmetry of revolution of the device would only be partial, the horizontal section of the assembly could for example have the elongated shape of two semicircles of identical diameters open towards one another and connected together by two sections right parallel,
• and those where the spacings of the two disks 2 ₁ and 6 would be controlled by means different from those described above, for example using a rotary cam mechanism and electrically actuated lever and linked to a rod of the kind the rod 20 above, this connection being provided with a clearance such that, when the mechanism is not actuated, the movements of the membrane 4 are sufficiently free.

Claims (10)

1. A hydraulic antivibration device designed to be interposed between two rigid elements, the structure of the device being circularly symmetrical about a vertical axis (X) and the device comprising: an annular rigid strength member (1) and a rigid rod (2) passing through said strength member, the strength member and the rod being suitable for being secured respectively to the two rigid elements that are to be united (9,10); an annular spring of elastomer (3) that withstands axial compression, resting against the strength member and the rod which passes through the spring; a leakproof flexible upper membrane (4) carried by the strength member and co-operating with at least one leakproof flexible annular wall (5) to define an enclosure disposed above the spring; an intermediate rigid partition (7) carried by the strength member, extending between the membrane and the annular wall and subdividing the inside of the enclosure into two chambers, a working bottom chamber (A) on the side of the spring, and a compensation chamber (B); a narrow passage (8) putting the two chambers permanently into communication with each other; a mass of liquid filling the two chambers and the narrow passage; a first disk (6) secured to the base of the annular wall; a second disk (2₁) secured to the head of the rod, the second disk being disposed immediately beneath the first disk and resting on the spring; and control means for causing at will the two disks (2₁,6) to move apart axially and subsequently to come back into contact.
2. An antivibratory device according to claim 1, characterized in that the control means are provided to axially displace the center of the membrane (4).
3. An antivibratory device according to any one of claims 1 and 2, characterized in that the control means (20-23) are electrically actuated.
4. An antivibratory device according to any one of the preceding claims, characterized in that the control means (13-15) bring a suction into play.
5. An antivibration device according to claim 4, in which one of the two rigid elements is a vehicle engine, characterized in that the suction is generated by operation of said engine, and in that application of the suction is servo-controlled to the engine idling while the vehicle is stationary.
6. An antivibration device according to any one of claims 4 and 5, characterized in that the means for controlling relative axial displacement of the two disks (2₁,6) comprise: a lid (11) covering the membrane (4) so as to co-operate therewith to form a gastight housing (12), a pipe connecting the inside of said housing to a source of suction (14), and a control valve (15) mounted on said pipe so as to control the connection between the housing and the source.
7. An antivibration device according to any one of the preceding claims, characterized in that it comprises means for detecting the frequency of the vibrations applied to one of the strength members and means for servo-controlling the mutual separation of the two disks (2₁,6) to the overpassing of a given threshold by said frequency.
8. An antivibration device according to any one of the preceding claims, characterized in that the intermediate partition is pierced by an orifice enabling the two chambers (A,B) to be put into communication with each other, and fitted with a valve member or membrane (16) whose displacements or deformations are of a limited amplitude that is at most equal to 1 mm.
9. An antivibration device according to claim 8, characterized in that it comprises means for detecting the amplitude of the vibrations applied to one of the strength members and means for servo-controlling the mutual separation of the two disks (2₁,6) to the overpassing of a given threshold by said amplitude.
10. An antivibration device according to any one of the preceding claims, characterized in that its hydraulic portion comprising the assembly constituted by the membrane (4), the wall (5), the disk (6) connected to said wall, and the intermediate partition (7) has an annular configuration about the axis (X), the disk connected to the wall then being in the form of a washer.

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